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Chapter 9 Implementing Association Relationships. Chapter 9 Topics. Review of Bradshaw Marina’s class diagram Implementing association relationships with one-to-one multiplicity between Java classes Navigating from one instance to another when there is a one-to-one relationship
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Chapter 9Implementing Association Relationships Chapter 9 - Implementing Association Relationships
Chapter 9 Topics • Review of Bradshaw Marina’s class diagram • Implementing association relationships with one-to-one multiplicity between Java classes • Navigating from one instance to another when there is a one-to-one relationship • Using the Vector class to create association relationships with one-to-many multiplicity between Java classes • Navigating one-to-many association relationships using methods of the Vector class • Creating and using an association class with Java Chapter 9 - Implementing Association Relationships
Reviewing Bradshaw Marina’s Class Diagram • See Figure 9-1 • Association relationships • Depict how instances of the classes are associated or connected to one another • Shown on the class diagram as lines connecting classes • Indicate that the system requires information about these associations Chapter 9 - Implementing Association Relationships
Reviewing Bradshaw Marina’s Class Diagram • Association relationships • Can be shown as: • Aggregation relationships • Strong association where one instance “contains” the other • E.g., town contains shopping centers or stores • Composition relationships • Strong association where one is composed of, or “part of” another • E.g., walls that are part of a building Chapter 9 - Implementing Association Relationships
Associating Customer with Boat: One-to-One Association Relationship • Each direction of the association relationship must be defined in Java • Mandatory / optional • Multiplicity • To implement in Java: • Use a reference variable of one class as an attribute of another class Chapter 9 - Implementing Association Relationships
Associating Customer with Boat: One-to-One Association Relationship • Modifying the Customer Class • To implement a one-to-one association with the Boat class: • Add an attribute to Customer that holds a reference to a Boat instance (Figure 9-3) • TesterOneA (Figure 9-4) • Tests one direction of association relationship • A Customer owns a Boat • Sequence diagram • Illustrates the interaction in TesterOneA Chapter 9 - Implementing Association Relationships
Associating Customer with Boat: One-to-One Association Relationship • Modifying the Boat Class • To implement a one-to-one association with the Customer class: (Figure 9-7) • Add an attribute to Boat that holds a reference to a Customer instance • Add accessor methods to establish the association relationship in both directions • TesterOneB (Figure 9-8) • Tests both directions of association relationship • A Customer owns a Boat • A Boat is owned by a Customer Chapter 9 - Implementing Association Relationships
Adding Capability to the Boat Class • Techniques to increase functionality • Make relationship mandatory rather than optional (pp. 291) • E.g., when Boat is instantiated, it could require that a Customer be specified • Thus, only Boats owned by Customers of the business would be accepted into the system • Modify the Boat’s tellAboutSelf method (pp. 292) • Return information about both Boat and Customer Chapter 9 - Implementing Association Relationships
Associating Dock and Slip: A One-to-Many Association Relationship • Dock / Slip Relationships • Slip and Dock relationship • A slip is attached to a dock • One-to-One relationship • Similar to Customer and Boat relationship • Dock and Slip relationship • A dock contains many slips • One-to-Many relationship • Requires different approach Chapter 9 - Implementing Association Relationships
Associating Dock and Slip: A One-to-Many Association Relationship • Introducing the Dock Class • Contains: • A Vector attribute • Implements the one-to-many relationship • A method that returns the Vector attribute reference Chapter 9 - Implementing Association Relationships
Associating Dock and Slip: A One-to-Many Association Relationship • Associating the Slip Class With Dock (Figure 9-15) • Modified much like Boat class to implement a mandatory one-to-one association relationship • Associates slip with dock • Further modified to also set up a relationship with a Boat • Associates slip with boat Chapter 9 - Implementing Association Relationships
Associating Dock and Slip: A One-to-Many Association Relationship • Testing the ‘Dock Contains Slips’ Association Relationship • TesterThreeA (Figure 9-16) • Tests both directions of association relationship • One-to-Many • A Dock has multiple Slips • One-to-one • A Slip resides in a Dock Chapter 9 - Implementing Association Relationships
Associating Dock and Slip: A One-to-Many Association Relationship • Adding the Boat and Customer Classes to the Example • To complete example (Figure 9-18): • Modify Boat to associate with a Slip • Add Customer class • TesterThreeB (Figure 9-19) • Provides a comprehensive test of associations • Sequence diagram (Figure 9-20) • Illustrates the interaction in TesterThreeB Chapter 9 - Implementing Association Relationships
Creating and Using an Association Class - Lease • Association class • Lease is an association between a customer and a slip, but with additional attributes to characterize the lease agreement • To implement (Figure 9-23): • Lease modified to include Slip and Customer reference attributes • Slip modified to include a Lease reference attribute • Class diagram (Figure 9-22) • Shows relationships between classes • TesterFour (Figure 9-26) • Provides a comprehensive test of overall Lease associations • Sequence diagram • Illustrates the interaction in TesterFour Chapter 9 - Implementing Association Relationships
